Presently, terrestrial digital television broadcast (which may hereafter be referred to as “terrestrial digital broadcast”) started also in Japan, and with this, a frequency band for use for the terrestrial digital broadcast is reconfigured. For example, a frequency band as large as 300 MHz that ranges from 470 MHz to 770 MHz is allocated and currently in use for the terrestrial digital broadcast in Japan.
However, there may be cases that the frequency band (or frequency bandwidth) allocated to the terrestrial digital broadcast is not used dependent on a time zone and a region. For example, some broadcast stations do not provide terrestrial digital broadcast late at night, early in the morning, etc. Also, there are cases that a frequency band (for example, a channel number “X”) allocated to terrestrial digital broadcast in one region (for example, Tokyo etc.) is not used as a frequency band for terrestrial digital broadcast in another region (for example, Osaka etc.).
Accordingly, a use of performing radio communication using a white space is presently taken into consideration. The white space signifies a frequency band (or frequency bandwidth) that is unused despite that a use license for a specific frequency band is granted for the purpose of a specific radio wave use service. For example, as described above, there is a frequency band that is not used dependent on a time zone and a region, and the use of such a frequency band by a secondary user to which the license is not granted is considered.
A frequency band available as a white space is, for example, a frequency of 1 GHz or lower, the use of which has various advantages including a flexible propagation characteristic, easy long-distance communication, etc. in comparison with a frequency band higher than 1 GHz.
In regard to such a white space, for example, radio communication using a database is currently under study in the U.S. FCC (Federal Communications Commission).
For example, information related to an available radio frequency and an available region is retained in the database, and a radio communication apparatus accesses the database as a secondary user to acquire the information of the available frequency band. Using the acquired frequency band, the radio communication apparatus performs radio communication in the region of concern. This enables prevention of radio communication interference between secondary users in the frequency band of the white space.
Meanwhile, as such a kind of technique, the following is disclosed, for example.
Namely, there is a technique in which a user sets a destination to a terminal apparatus, and when the user selects a content desired to view during traveling, the terminal apparatus searches for a shortest route that produces a poor reception state of the content. In the case of the above technique, the terminal apparatus preserves a broadcast reception level, information of a road section that produces a poor reception state of the content and reception channel information, as preservation information, so that can share the preservation information among terminal apparatuses or download the above preservation information from a server and a mobile terminal.
Further, there is a technique in which a mobile information terminal accesses a center server system to acquire local information instructed by an operator, so as to store the genre of the local information and effective range information indicative of a search region range. In this case, for example, when the search of local information is instructed by the operator in another opportunity, the mobile information terminal is configured to prevent duplicated downloading of the same local information by use of the stored effective range information.